Multi-site design requires careful planning. Mistakes create split-brain scenarios.
Stretched VLANs: Extending Layer across sites creates risks. A broadcast storm affects both sites.
Asymmetric traffic: Traffic entering one site may exit another. This can waste expensive WAN bandwidth.
Latency constraints: Synchronous replication needs sub-ms latency. VM migration works best under ms.
Failure domains: Keep them small. If Site A fails, Site B should continue. Avoid dependencies where one site needs the other.